Embryonic loss in iatrogenic multiples.

Spontaneous reduction of multiple gestational sacs occurs less often in pregnancies conceived as a result of ovulation induction and assisted reproductive technology compared with spontaneously conceived multiple pregnancies. Whereas most spontaneous multiple pregnancies are twin gestations, a higher proportion of multiple pregnancies that result from ovulation induction and assisted reproductive technology are triplet and higher-order gestations. Recent evidence, described in this article, indicates that although twin and higher-order multiple gestations found on initial ultrasound subsequently may undergo spontaneous reduction to singletons or twins, there may be important consequences for the outcome of the surviving fetus or fetuses.